geoserver+openlayers实例

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geowebcache为开源地图Title发布，在线服务．geowebcache会根据你的配置信息，把相应的地图图层切好图，存放在磁盘中，然后在使用openlayer加载地图服务的时候，把地图服务的地址指向geowebcache，geowebcache接收到这些请求后，会根据请求的位置和比例尺在切片目录中找到对应的瓦片，然后返回给你，省去了动态生成地图的过程，速度大幅度提高，而且由于请求的图片资源是事先生成好的，浏览器加载这些图片之后，下一次再去请求同样的图片，就会从浏览器的缓存中拉去，速度进一步提高！

下面说一下geowebcache的配置使用。首先下载war包，在tomcat中解压后，会在WEB-INF目录下找到一系列配置文件，先找到web.xml，然后在web-app根元素下添加：

<context-param>    <param-name>GEOWEBCACHE_CACHE_DIR</param-name>    <param-value>D:/data/cache</param-value></context-param>

param-value的值就是你要存放geowebcache瓦片的位置，配置好这里，重启tomcat，你会发现在你的瓦片目录下生成了一些文件，其中就有geowebcache.xml，这个文件是geowebcache配置的关键所在，以下是这个文件的配置信息：

<?xml version="1.0" encoding="utf-8"?><gwcConfiguration xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  xmlns="http://geowebcache.org/schema/1.5.3"  xsi:schemaLocation="http://geowebcache.org/schema/1.5.3 http://geowebcache.org/schema/1.5.3/geowebcache.xsd">  <version>1.5.3</version>  <backendTimeout>120</backendTimeout>  <serviceInformation>    <title>GeoWebCache</title>    <description>GeoWebCache is an advanced tile cache for WMS servers.It supports a large variety of protocols and      formats, including WMS-C, WMTS, KML, Google Maps and Virtual Earth.</description>    <keywords>      <string>WFS</string>      <string>WMS</string>      <string>WMTS</string>      <string>GEOWEBCACHE</string>    </keywords>    <serviceProvider>      <providerName>xx</providerName>      <providerSite>http://blog.csdn.net/xx</providerSite>      <serviceContact>        <individualName>xx</individualName>        <positionName></positionName>        <addressType></addressType>        <addressStreet>xx</addressStreet>        <addressCity>xx</addressCity>        <addressAdministrativeArea>xx</addressAdministrativeArea>        <addressPostalCode>010010</addressPostalCode>        <addressCountry>中国,China</addressCountry>        <phoneNumber></phoneNumber>        <faxNumber></faxNumber>        <addressEmail></addressEmail>      </serviceContact>    </serviceProvider>    <fees>NONE</fees>    <accessConstraints>NONE</accessConstraints>  </serviceInformation>  <gridSets>    <!-- Grid Set Example, by default EPSG:900913 and EPSG:4326 are defined -->    <gridSet>      <!-- This does not have to be an EPSG code, you can also have multiple gridSet elements per SRS -->      <name>EPSG:4326</name>      <srs>        <number>4326</number>      </srs>      <extent>        <coords>          <double>73.45100463600005</double>          <double>18.16324718800007</double>          <double>134.976797647</double>          <double>53.53194315200005</double>        </coords>      </extent>      <scaleDenominators>        <double>25000000</double>        <double>1000000</double>        <double>100000</double>        <double>25000</double>      </scaleDenominators>      <tileHeight>256</tileHeight>      <tileWidth>256</tileWidth>    </gridSet>  </gridSets>  <layers>    <wmsLayer>      <name>china</name>      <mimeFormats>        <string>image/gif</string>        <string>image/jpeg</string>        <string>image/png</string>        <string>image/png8</string>      </mimeFormats>      <wmsUrl>        <string>http://200.200.200.220:8888/geoserver/wms</string>      </wmsUrl>      <wmsLayers>geoserver:china</wmsLayers>    </wmsLayer>  </layers>  </gwcConfiguration>

配置好上面的信息之后，进入： http://localhost:8080/geowebcache/demo ，点击" Reload Configuration

"重新读取配置信息,如下所示：

如果配置信息没错，你会发现，你所配置的图层信息已经显示在这个页面上了，点击 “Seed this layer”，然后你需要输入下面这些信息：

设置好，点submit就开始切图了。在资源管理器中打开，如下图：

配置完成以后，就是如何在地图中显示了，下面是显示的源代码：

<pre name="code" class="html"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><title>china EPSG:4326 image/png</title><link rel="stylesheet" type="text/css" href="http://200.200.200.220/OpenLayers-2.12/theme/default/style.css"/><style type="text/css">  body { font-family: sans-serif; font-weight: bold; font-size: .8em; }  body { border: 0px; margin: 0px; padding: 0px; }  #map { width: 100%; height: 100%; border: 0px; padding: 0px; }</style><script type="text/javascript" src="http://200.200.200.220/OpenLayers-2.12/OpenLayers.js"></script>  <script type="text/javascript" src="http://200.200.200.220/OpenLayers-2.12/lib/OpenLayers/Lang/zh-CN.js"></script><script type="text/javascript">                 var map, demolayer;                                                                          OpenLayers.DOTS_PER_INCH = 90.71428571428572;  OpenLayers.Util.onImageLoadErrorColor = 'transparent';  function init(){    var mapOptions = {       resolutions: [0.703125, 0.3515625, 0.17578125, 0.087890625, 0.0439453125, 0.02197265625,         0.010986328125, 0.0054931640625, 0.00274658203125, 0.001373291015625, 6.866455078125E-4,         3.4332275390625E-4, 1.71661376953125E-4, 8.58306884765625E-5, 4.291534423828125E-5,         2.1457672119140625E-5, 1.0728836059570312E-5, 5.364418029785156E-6, 2.682209014892578E-6,         1.341104507446289E-6, 6.705522537231445E-7, 3.3527612686157227E-7      ],      projection: new OpenLayers.Projection('EPSG:4326'),      maxExtent: new OpenLayers.Bounds(-180.0,-90.0,180.0,90.0),      units: "degrees",      controls: []    };    map = new OpenLayers.Map('map', mapOptions );        map.addControl(new OpenLayers.Control.PanZoomBar({        position: new OpenLayers.Pixel(2, 15)    }));    map.addControl(new OpenLayers.Control.Navigation());    map.addControl(new OpenLayers.Control.Scale($('scale')));    map.addControl(new OpenLayers.Control.MousePosition({element: $('location')}));        demolayer = new OpenLayers.Layer.WMS(      "china","http://200.200.200.220:8080/geowebcache/service/wms",      {layers: 'china', format: 'image/png' },      { tileSize: new OpenLayers.Size(256,256)}    );    map.addLayer(demolayer);    map.zoomToExtent(new OpenLayers.Bounds(73.45100463600005, 18.16324718800007,       134.976797647, 53.53194315200005)    );  }</script></head><body onLoad="init()">  <div id="map"></div></body></html>

显示的结果如下：

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